Is there any way (from within an on_import plugin) to actually 'cancel' the import of an ebook? I know I can raise an error (or return 'None'), but that just means that the original ebook will still be imported unmolested.

I'm not sure if it's even possible (or if I'm missing the obvious), but I wouldn't want it to completely abort a multiple ebook import... but rather, have the ability to say; "this particular ebook doesn't meet my requirements and should be completely skipped."